Work in LMB has led the way towards the ambitious goal where stem cells can be used to replace tissue damaged by neurodegenerative diseases that cause the loss of neurons or glial cells. We have previously demonstrated that stem cells derived from the fetal brain can generate neurons that secrete the neurotransmitter dopamine but these cells can provide unlimited numbers of these neurons. In the last year we have continued to develop embryonic stem (ES) cells as a source of dopamine neurons. These are the type of neuron lacking in Parkinson?s patients and these neurons have not previously been obtained in such large numbers. Our procedure involves guiding ES cells through the several stages that normally occur over three months of human development. Because this is achieved in tissue culture we can manipulate the environment of the cells by adding known signal proteins that enhance the differentiation of the neurons we need. In the last year we made the surprising finding that by modifying this method we were able to generate large numbers of insulin producing cells normally found in the pancreatic islets. Indeed this strategy generates the several cell types found in pancreatic islets and these different cells assemble in tissue culture into structures that resemble the islets and release insulin. This finding has important implications in diabetes. In another series of experiments we collaborated with others to show that adult hematopoietic stem cells found in the bone marrow showed remarkable abilities to regenerate the injured heart. These experiments are gratifying because they show that the techniques we developed for studying the brain have important clinical implications in neurology and in other areas of medicine.